Association between genetic factors and molar-incisor hypomineralisation or hypomineralised second primary molar: A systematic review

Influence of maternal health status during pregnancy and the child´s medical history on molar-incisor hypomineralization in a group of Spanish children (aged 6-14 years): a retrospective case-control study

BACKGROUND

Molar-incisor hypomineralization (MIH) is a qualitative enamel defect that is highly prevalent in children. It has been reported that patients with MIH have higher caries occurrence with an increased need and frequency of dental treatment compared to patients without MIH. The objective of this study was to analyze the association between MIH and a series of factors related to maternal health status during pregnancy and children´s medical history in early childhood.

METHODS

A retrospective study of cases (patients with MIH) and controls (patients without MIH) was designed between 2023 and 2024. A total of 280 children (cases = 140; controls = 140) aged 6 to 14 years (138 boys and 142 girls) were examined according to the European Academy of Pediatric Dentistry (EAPD) criteria for MIH. A survey was carried out with mothers regarding the potential exposure of their children to etiological factors of MIH. Possible prenatal and postnatal etiological factors were obtained through a personal interview with the patients' mothers. The statistical analysis was carried out with the contrast test and the chi-square test.

RESULTS

During pregnancy, folic acid consumption, alcohol intake, systemic viral and/or bacterial infections, and gestational diabetes were statistically significantly related to MIH, as were breastfeeding, asthma, and corticosteroid consumption during childhood.

CONCLUSIONS

Although there are different factors that may have statistically significant relationships with MIH, they cannot be predicted. Therefore, longitudinal studies, with a large sample size, are needed to determine the influence of prenatal and postnatal factors on the prevalence and severity of MIH in children.

Genetic polymorphisms associated with developmental defects of enamel: A systematic review

BACKGROUND

Polymorphisms in genes related to enamel formation and mineralization may increase the risk of developmental defects of enamel (DDE).

AIM

To evaluate the existing literature on genetic polymorphisms associated with DDE.

DESIGN

This systematic review was registered in the PROSPERO (CRD42018115270). The literature search was performed in PubMed, Scopus, Web of Science, LILACS, BBO, Cochrane Library, and in the gray literature. Observational studies assessing the association between DDE and genetic polymorphism were included. The Newcastle-Ottawa Scale was used to assess the risk of bias.

RESULTS

One thousand one hundred and forty-six articles were identified, and 28 met the inclusion criteria. Five studies presented a low risk of bias. Ninety-two genes related to enamel development, craniofacial patterning morphogenesis, immune response, and hormone transcription/reception were included. Molar-incisor hypomineralization (MIH) and/or hypomineralization of primary second molars (HPSM) were associated with 80 polymorphisms of genes responsible for enamel development, immune response, morphogenesis, and xenobiotic detoxication. A significant association was found between the different clinical manifestations of dental fluorosis (DF) with nine polymorphisms of genes responsible for enamel development, craniofacial development, hormonal transcription/reception, and oxidative stress. Hypoplasia was associated with polymorphisms located in intronic regions.

CONCLUSION

MIH, HPSM, DF, and hypoplasia reported as having a complex etiology are significantly associated with genetic polymorphisms of several genes.

Association of defects of enamel with polymorphisms in the vitamin D receptor and parathyroid hormone genes

This cross-sectional study aimed to investigate the association between developmental defects of enamel (DDE) and single nucleotide polymorphisms (SNPs) in the genes encoding the vitamin D receptor (VDR) and parathyroid hormone (PTH). Orthodontic patients receiving treatment at a dental school were selected through convenience sampling. Intra-oral photographs were used to assess DDE, which were classified according to the criteria proposed by Ghanim et al. (2015) by a single calibrated examiner (Kappa>0.80). Enamel hypoplasia, molar-incisor hypomineralization (MIH), hypomimineralized second primary molar (HSPM), and non-MIH/HSPM demarcated opacities were considered for the analysis. Genomic DNA was extracted from buccal cells. The SNPs in VDR (rs7975232) and PHT (rs694, rs6256, and rs307247) were genotyped using real-time polymerase chain reactions (PCR). Statistical analyses were performed using the PLINK software (version 1.03, designed by Shaun Purcell, EUA). Chi-square or Fisher's exact tests were performed at a significance level of 5%. Ninety-one (n=91) patients (49 females and 42 males) (mean age of 14.1±5.8 years) were included. The frequency of DDE was 38.5% (35 patients). Genotype distributions were in Hardy-Weinberg equilibrium. No significant statistical association was found between DDE and the SNPs evaluated. A borderline association (p=0.09) was observed between DDE and the CC haplotype for SNP rs7975232 in VDR. In conclusion, the selected SNPs in VDR and PTH genes were not associated with DDE in the studied samples.

Dentin hypersensitivity and toothache among patients diagnosed with Molar-Incisor Hypomineralization: A systematic review and meta-analysis

OBJECTIVES

To determine the prevalence of dentin hypersensitivity (DH) and toothache in patients with Molar-Incisor Hypomineralization (MIH); and evaluate whether patients with MIH have greater likelihood of presenting DH/toothache than controls.

DATA

Studies evaluating DH/toothache in patients with MIH were included. Studies focusing on other enamel defects were excluded.

SOURCES

Eight databases, including grey literature, were searched in January 2024.

STUDY SELECTION

The methodological quality of studies was assessed using the Joanna Briggs Institute checklist for Cross-sectional studies. Proportion and association meta-analyses, subgrouped by diagnostic methods, were conducted. The certainty of evidence was assessed using GRADE approach.

RESULTS

Fifteen studies were included in the qualitative analysis and fourteen in the meta-analyses. Two studies fulfilled all items of the methodological quality checklist. The overall prevalence of DH/toothache among patients with MIH was 45 %. Prevalence rates of 30 %, 47 %, and 55 % were estimated based on proxy reports, self-reports, and air stimulation, respectively. The overall prevalence of DH/toothache per tooth was 22 %, ranging from 16 % to 29 % according to the diagnostic method. Patients with MIH demonstrated higher likelihood of presenting proxy reports of DH/toothache compared to those without MIH (OR: 1.51, 95 % CI [1.23-1.85], P < 0.01, I2: 0 %). The certainty of evidence was very low, mainly due to the low methodological quality of included studies and high inconsistency.

CONCLUSIONS

The global prevalence of DH/toothache was 22 %, per tooth, and 45 % per patient. Estimates vary according to diagnostic methods. Patients with MIH showed higher likelihood of presenting proxy reports of DH/toothache than controls.

CLINICAL SIGNIFICANCE

This systematic review contributes valuable information to the dental literature by assessing the prevalence and associated factors of DH/toothache in patients with MIH. The findings can guide future research, inform clinical practices and public policy makers, and ultimately improve the management of oral health of patients with MIH.

REGISTRATION

PROSPERO CRD42023432805.

Association of Three Genetic Loci with Molar Incisor Hypomineralization in Polish Children

BACKGROUND

Molar incisor hypomineralization (MIH) is a qualitative, demarcated enamel defect of hypomineralization affecting one to four first permanent molars, often with incisor involvement. Its etiology is complex. However, evidence suggests the influence of genetic factors, potentially including the single nucleotide polymorphisms (SNPs) rs2889956, rs4811117 and rs13058467, which were previously linked to MIH in a genome-wide association study of German children. The aim was to replicate analyses of possible associations between the SNPs and molar incisor hypomineralization in Polish children.

METHODS

The final study group consisted of 778 children aged 126-168 months old. Saliva samples were taken, and genomic DNA was extracted and genotyped using beadchip microarrays.

RESULTS

Among the 778 subjects, there were 68 (8.7%) subjects with MIH and 710 (91.3%) subjects without MIH. There were no significant differences in distributions in age, sex, or the frequency of caries in permanent dentition between the MIH and non-MIH groups. The rs2889956, rs4811117, and rs13058467 genotype distributions in the studied group conformed to the expected Hardy-Weinberg equilibria, and there were no significant differences in the distributions of their alleles or genotypes between the MIH and non-MIH groups.

CONCLUSION

Our replication study did not confirm highly significant associations between the single nucleotide polymorphisms rs2889956, rs4811117, and rs13058467 with molar incisor hypomineralization in Polish children.